1 2 TODO
3~~~~~~
4Please pick something while reading :)
5 6- Convert interrupt handler to per-ep-thread-irq
7 8 As it turns out some DWC3-commands ~1ms to complete. Currently we spin
9 until the command completes which is bad.
10 11 Implementation idea:
12 - dwc core implements a demultiplexing irq chip for interrupts per
13 endpoint. The interrupt numbers are allocated during probe and belong
14 to the device. If MSI provides per-endpoint interrupt this dummy
15 interrupt chip can be replaced with "real" interrupts.
16 - interrupts are requested / allocated on usb_ep_enable() and removed on
17 usb_ep_disable(). Worst case are 32 interrupts, the lower limit is two
18 for ep0/1.
19 - dwc3_send_gadget_ep_cmd() will sleep in wait_for_completion_timeout()
20 until the command completes.
21 - the interrupt handler is split into the following pieces:
22 - primary handler of the device
23 goes through every event and calls generic_handle_irq() for event
24 it. On return from generic_handle_irq() in acknowledges the event
25 counter so interrupt goes away (eventually).
26 27 - threaded handler of the device
28 none
29 30 - primary handler of the EP-interrupt
31 reads the event and tries to process it. Everything that requires
32 sleeping is handed over to the Thread. The event is saved in an
33 per-endpoint data-structure.
34 We probably have to pay attention not to process events once we
35 handed something to thread so we don't process event X prio Y
36 where X > Y.
37 38 - threaded handler of the EP-interrupt
39 handles the remaining EP work which might sleep such as waiting
40 for command completion.
41 42 Latency:
43 There should be no increase in latency since the interrupt-thread has a
44 high priority and will be run before an average task in user land
45 (except the user changed priorities).
46